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  • Publication
    Improved seismic profiling by minimally invasive multimodal surface wave method with standard penetration test source (MMSW-SPT)
    (Oxford University Press on behalf of The Royal Astronomical Society 2016, 2017-03) Lin, Shibin ; Ashlock, Jeramy ; Civil, Construction and Environmental Engineering
    Surface waves propagating in layered media inherently possess multimodal dispersion characteristics. However, traditional surface wave testing methods employing measurements at the free surface usually capture only a single apparent dispersion curve, especially when using short geophone arrays common to near surface and geotechnical-scale investigations. Such single-mode or fragmented multimode apparent dispersion curves contain only a fraction of the possible dispersion information, thus limiting the accuracy of inverted profiles. To enable more robust measurement of higher Rayleigh-wave modes, a recently developed hybrid minimally invasive multimodal surface wave method is combined herein with the widely used geotechnical standard penetration test (SPT), which is employed as a practical and ubiquitous downhole source. Upon superimposing surface wave dispersion data for a range of SPT impact depths within the soil, higher modes can be measured more consistently and reliably relative to traditional non-invasive testing methods. As a result, misidentification of multiple dispersion modes can be practically eliminated, significantly improving the accuracy and certainty of inversion results.
  • Publication
    Cybersickness Detection through Head Movement Patterns: A Promising Approach
    (arXiv, 2024-02-26) Salehi, Masoud ; Javadpour, Nikoo ; Beisner, Brietta ; Sanaei, Mohammadamin ; Gilbert, Stephen ; Industrial and Manufacturing Systems Engineering
    Despite the widespread adoption of Virtual Reality (VR) technology, cybersickness remains a barrier for some users. This research investigates head movement patterns as a novel physiological marker for cybersickness detection. Unlike traditional markers, head movements provide a continuous, non-invasive measure that can be easily captured through the sensors embedded in all commercial VR headsets. We used a publicly available dataset from a VR experiment involving 75 participants and analyzed head movements across six axes. An extensive feature extraction process was then performed on the head movement dataset and its derivatives, including velocity, acceleration, and jerk. Three categories of features were extracted, encompassing statistical, temporal, and spectral features. Subsequently, we employed the Recursive Feature Elimination method to select the most important and effective features. In a series of experiments, we trained a variety of machine learning algorithms. The results demonstrate a 76% accuracy and 83% precision in predicting cybersickness in the subjects based on the head movements. This study contribution to the cybersickness literature lies in offering a preliminary analysis of a new source of data and providing insight into the relationship of head movements and cybersickness.
  • Publication
    Predicting thermal performance of a mass concrete foundation - A field monitoring case study
    (Elsevier Ltd., 2019-10-30) Sargam, Yogiraj ; Faytarouni, Mahmoud ; Riding, Kyle ; Wang, Kejin ; Jahren, Charles ; Shen, Jay ; Civil, Construction and Environmental Engineering
    High-temperature differentials in a mass concrete structure pose great risks of temperature-induced stresses and cracking. Prior knowledge of temperature development within such a structure is essential. In this context, this paper presents a case study in which the construction of a mass concrete bridge foundation in Iowa, USA was investigated and a computer program, ConcreteWorks (CW), was used to predict its overall thermal performance with an aim to prevent thermal cracking. The properties of mass concrete mixes, required as CW inputs, were measured through isothermal and semi-adiabatic calorimetry tests. The temperature development profile, temperature differential, maturity, and compressive strength of the mixes were predicted and compared with those measured through the real-time monitoring of the bridge foundation. It was observed that CW predictions match well with their corresponding measured values. Three locations, core, top, and the face nearest to the core of the foundation, were found to be critical points for high temperature differentials. A sensitivity analysis, analyzing the effects of various mass concrete parameters, is also presented. The results provided clear insights into the temperature development of concrete with complex material compositions and environmental conditions. CW is a useful tool in developing thermal control plan for mass concrete projects.
  • Publication
    Estimating demand systems with corner solutions: the performance of Tobit-based approaches
    (Taylor & Francis Group, 2024-02-12) Ban, Kyunghoon ; Lence, Sergio ; Economics
    Since Tobin’s (1958) innovative censored dependent variable framework, practitioners have been facing a clear trade-off between flexibility and theoretical plausibility in modeling consumers’ preferences in the presence of zero consumptions; the Kuhn-Tucker (or virtual price) approach is rigorously based on the economic choice theory but cannot be applied to complex and flexible demand systems, whereas the Tobit-based approach can be applied to any class of demand systems but is deficient in the theoretical foundations on the underlying preferences behind the observed choices. Hence, we assess the performance of three Tobit-based approaches (simple, correlated, and Amemiya-Tobin) and explore the extent of possible biases in elasticity estimates to provide reasonable criteria for model selection. Our analysis concludes that theoretical restrictions implied by the choice theory are essential to the Tobit model and improve its ability to capture the true underlying elasticities and mitigate overrejections. However, the performance of the Tobit models gradually deteriorates as the number of zero consumptions increases; the average rejection rate against the true elasticity values increases substantially as we have more zero consumptions. We illustrate the performance differences among the three Tobit models by applying them to the estimation of demand for fruits and vegetables.
  • Publication
    Crossroads on the Silk Road: accounts of a U.S.-American faculty member’s culture shock and adaptation in Uzbekistan
    (Taylor and Francis, 2024-03-01) Coffelt, Tina ; English
    The knowledge of and experience with culture shock and intercultural communication come under analysis in this autoethnography of a U.S.-American faculty member’s Fulbright teaching experience in Uzbekistan. As a relatively new country couched under the blanket of Russian and Chinese influence, Uzbekistan strives to shift its economy, language, and geopolitical connections toward the West. Cultural knowledge about Uzbekistan is likewise still hidden behind the Uzbek and Russian languages, leaving English speakers from the West with few resources to engage in predeparture uncertainty reduction. This manuscript chronicles the early days of a sojourn of a faculty member who had cognitive knowledge of intercultural communication concepts but had no immersion experiences in which to test her abilities to adapt. Anxiety uncertainty management theory offers some insight into the culture shock and adaptation experienced by this faculty member. The study benefits teachers who may enter this or similar cultures, teachers who instruct with an interpreter, and anyone seeking cultural information about Uzbekistan.